The applicant proposes to study the mechanism of activation of c-myc at a molecular level in both Burkitt's lymphoma and transformed lymphomas with the t(8;14) translocation. The goal is to reach a better understanding of the mechanisms of malignant transformation of B cells. A. Identification of the molecular mechanisms of transcriptional control of the c-myc gene in B cells. In vivo footprinting and in vitro protein-DNA binding studies will be used to locate regulatory regions important for c-myc expression in normal B cells and in B cell lines that do not contain the t(8;14) translocation. The identity of the proteins that bind in vivo will be determined by a technique of UV crosslinking and immunoprecipitation followed by hybridization analysis. Functional assessment of the sites will be performed with transient transfection experiments in B cell lines. B. Identification of the molecular mechanisms of transcriptional control of the c-myc gene in Burkitt's lymphomas. Conditions have been optimized for the separation of the translocation from the normal c-myc gene in several Burkitt's cell lines. Differences in the binding of transcription factors between the two alleles have been found and these studies will be continued. The identification and characterization of the proteins that bind in vivo will be determined as described in A. The methylation status of each allele will be compared. C. Identification of the molecular mechanisms of transcriptional control of the c-myc and bcl-2 genes in transformed lymphomas and their low grade counterparts. The deregulation of both c-myc and bcl-2 by the immunoglobulin locus will be studied as outlined in B. D. Effect on c-myc expression of mutations identified in the regulatory regions. The effects of any mutations on the binding of regulatory proteins will be investigated by in vivo and in vitro studies. E. Role of the immunoglobulin locus in the activation of c-myc expression. Model constructs which reproduce the c-myc translocations will be constructed and used to define the important regions of the immunoglobulin locus. The successful completion of this proposal will represent the first instance where the molecular mechanisms involved in the transcriptional activation of an oncogene by translocation are known. The transcription factors that are required for the activation of c-myc will be identified and the regions of the immunoglobulin locus which are responsible for this will be defined.